Method and apparatus for power saving in client terminals

ABSTRACT

In any cellular communication the network transmits broadcast information with some periodicity which is defined by the network parameters. The client terminal must acquire this system information in order to access the services from the network. The time required by the client terminal to acquire all the necessary system information to initiate network access may depend on the scheduling of the system information broadcast by the network. In some cases the scheduling information about the system information may be described in another system information message whose schedule may be fixed or known a priori. Conventional method of decoding the complete system information may involve decoding attempt for all the possible instances of transmission of the system information. A method and apparatus are disclosed that enables acquisition of the system information based on stored known instances of system information transmission. This results in reduced power consumption at the client terminal.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 14/707,390, filed on May 8, 2015, the disclosure of which isincorporated herein by reference.

As shown in FIG. 1, a wireless communication system 10 compriseselements such as client terminal or mobile station 12 and base stations14. Other network devices which may be employed, such as a mobileswitching center, are not shown. In some wireless communication systemsthere may be only one base station and many client terminals while insome other communication systems such as cellular wireless communicationsystems there are multiple base stations and a large number of clientterminals communicating with each base station.

As illustrated, the communication path from the base station (BS) to theclient terminal direction is referred to herein as the downlink (DL) andthe communication path from the client terminal to the base stationdirection is referred to herein as the uplink (UL). In some wirelesscommunication systems the client terminal or mobile station (MS)communicates with the BS in both DL and UL directions. For instance,this is the case in cellular telephone systems. In other wirelesscommunication systems the client terminal communicates with the basestations in only one direction, usually the DL. This may occur inapplications such as paging.

The base station to which the client terminal is communicating with isreferred as the serving base station. In some wireless communicationsystems the serving base station is normally referred as the servingcell. The terms base station and a cell may be used interchangeablyherein. In general, the cells that are in the vicinity of the servingcell are called neighbor cells. Similarly, in some wirelesscommunication systems a neighbor base station is normally referred as aneighbor cell.

The 3GPP LTE wireless communication system air interface is organizedinto radio frames, subframes, and Orthogonal Frequency DivisionMultiplexing (OFDM) symbols as shown in FIG. 2. Each radio framecomprises ten subframes numbered from subframe 0 to subframe 9. Theradio frame duration is 10 ms and the subframe duration is 1 ms. In 3GPPLTE wireless communication system, a BS is referred to as evolved NodeB(eNB).

As per 3GPP LTE wireless communication system specifications, each cellbroadcasts the access information about the system which is required forthe client terminals to receive service. The system information isorganized into the MasterInformationBlock (MIB) and a number ofSystemInformationBlocks (SIBs). The MIB includes a limited number ofessential parameters that are required to acquire other systeminformation from a cell.

As per 3GPP LTE wireless communication system specifications, the MIB istransmitted on the Physical Broadcast Channel (PBCH) in subframe 0 asshown in FIG. 2. The MIB uses a fixed schedule with a periodicity of 40ms and repetitions made within 40 ms. The first transmission of the MIBis scheduled in subframe #0 of radio frames for which the system framenumber (SFN) mod 4=0, and repetitions are scheduled in subframe #0 ofall other radio frames within the 40 ms window. An example of this isshown in FIG. 3.

As per 3GPP LTE wireless communication system specifications, the SIB1is transmitted on a fixed schedule over the Physical Downlink SharedChannel (PDSCH) with a periodicity of 80 ms and repetitions made withineach 80 ms window. The first transmission of SIB1 may be scheduled insubframe #5 of radio frames for which the SFN mod 8=0, and repetitionsare scheduled in subframe #5 of all other radio frames for which SFN mod2=0. An example of this is shown in FIG. 4.

As per 3GPP LTE wireless communication system specifications, the SIBsother than SIB1 are transmitted in SystemInformation (SI) messages andmapping of SIBs to SI messages is flexibly configurable by theInformation Element (IE) SchedulingInformation included in the SIB 1.Each SIB must be contained only in a single SI message. Only SIBs havingthe same scheduling requirement (periodicity) can be mapped to the sameSI message. The SIB2 is always mapped to the SI message that correspondsto the first entry in the list of SI messages in SchedulingInformation.There may be multiple SI messages transmitted with the same periodicity.SIB1 and all SI messages are transmitted on PDSCH. An example of themapping of SIBs to SI messages is shown in FIG. 5.

As per 3GPP LTE wireless communication system specifications, the SImessages are transmitted within periodically occurring time window,referred to as SI-window, using dynamic scheduling. Each SI message isassociated with an SI-window and the SI-window of different SI messagesdo not overlap, i.e., within one SI-window only the corresponding SI istransmitted. The length of the SI-window is common for all SI messages,and is configurable. Within the SI-window, the corresponding SI messagemay be transmitted a number of times in any subframe other thanMulticast-Broadcast Single Frequency Network (MBSFN) subframes, uplinksubframes in TDD, and subframe #5 of radio frames for which SFN mod 2=0.The client terminal acquires the detailed time-domain scheduling fromdecoding SIB1 which configures the SI-window length and the transmissionperiodicity for the SI messages. An example of the mapping of the SImessages to SI-windows is shown in FIG. 6. Each rectangular box in FIG.6 represents one subframe. The shaded boxes are used to indicate thesubframes that are used for scheduling SI messages within an SI-window.

As per 3GPP LTE wireless communication system specifications, the SImessages may be transmitted in the SI-window using dynamic scheduling bythe eNB. The SI messages may be transmitted in all subframes inSI-window or the SI messages may be transmitted in some subframes in theSI-window. The eNB may have different SI message transmission schedulingin each SI-window for different SI messages.

Conventional methods depend on successfully decoding the SIB1 first toacquire the detailed time-domain scheduling information for other SImessages, e.g. frequency-domain scheduling, used transport format beforedecoding other SIs and attempt to decode SI in all subframes inSI-Window.

BRIEF SUMMARY

In accordance with an aspect of the present invention, a method fordecoding system information may include determining, by a processingdevice, whether a system information block (SIB) Presence Bitmap for acurrently selected base station is stored in a memory of a wirelesscommunication device associated with the processing device; andcontrolling, by the processing device, SIB decoding for the currentlyselected base station according to either a SIB Presence Bitmap of alast serving base station or the SIB Presence Bitmap for the currentlyselected base station stored in the memory selected as a selected SIBPresence Bitmap, based on a result of the determining whether the SIBPresence Bitmap is in the memory.

In one alternative, the SIB decoding is performed for radio frames andsubframes according to the selected SIB Presence Bitmap.

In one alternative, the method may further include determining, by theprocessing device, whether the SIB decoding is successful; and wherein,when the decoding is determined to be successful, updating, by theprocessing device, the SIB Presence Bitmap for the currently selectedbase station stored in the memory according to detection and decodingstatus in radio frames and subframes in which a SIB was transmitted bythe currently selected base station.

In one alternative, the method may further include, when the SIBdecoding is determined to be unsuccessful, determining, by theprocessing device, whether SIB decoding was attempted for all instancesof the SIB within a SIB periodicity.

In one alternative, the method may further include, when the SIBdecoding for the all instances of the SIB is determined to have beenattempted, controlling, by the processing device, decoding a SI messagefor the currently selected base station according to schedulinginformation extracted from the SIB transmitted by the currently selectedbase station.

In one alternative, the method may further include, when the SIBdecoding for the all instances of the SIB is determined not to have beenattempted, controlling, by the processing device, SIB decoding for allremaining SIB instances within the SIB periodicity, and after the SIBdecoding is performed for the all remaining SIB instances, determining,by the processing device, whether the SIB decoding is successful.

In one alternative, the method may further include, when the SIBdecoding is successful after the SIB decoding is performed for the allremaining SIB instances, updating, by the processing device, the SIBPresence Bitmap for the currently selected base station stored in thememory according to detection and decoding status in radio frames andsubframes in which the SIB was transmitted by the currently selectedbase station, extracting from the decoded SIB, by the processing device,scheduling information for SI messages, and controlling, by theprocessing device, decoding of a specific SI message for the currentlyselected base station according to the scheduling information.

In one alternative, the method may further include controlling, by theprocessing device, decoding of a SI message for the currently selectedbase station according to scheduling information for SI messagesextracted from a SIB decoded from the currently selected base station;determining, by the processing device, whether a SI subframe bitmap(subframebmp) for a specific SI message selected for decoding for thecurrently selected base station is stored in the memory; andcontrolling, by the processing device, SI message decoding for thespecific SI message for the currently selected base station according toa SI subframebmp of the last serving base station or the SI subframebmpfor the currently selected base station stored in the memory selected asa selected SI subframebmp, based on a result of the determining whetherthe SI subframebmp is in the memory.

In one alternative, the SI message decoding of the specific SI messagemay be performed for radio frames and subframes according to theselected SI subframebmp.

In one alternative, the method may further include: determining, by theprocessing device, whether the SI message decoding is successful; andwherein, when the SI message decoding is determined to be successful,updating, by the processing device, the SI subframebmp for the specificSI message of the currently selected base station stored in the memoryaccording to detection and decoding status in radio frames and subframesin which the specific SI message was transmitted by the currentlyselected base station.

In one alternative, the method may further include, when the SI messagedecoding is determined to be unsuccessful, determining, by theprocessing device, whether SI message decoding is attempted for allsubframe instances of the SI message within an SI window.

In one alternative, the method may further include, when the SI messagedecoding for the all subframe instances is determined to be notattempted, controlling, by the processing device, SI message decodingfor remaining subframe instances within the SI window where the SImessage decoding was not attempted, and after the SI message decoding isattempted for the remaining subframe instances, determining, by theprocessing device, whether the SI message decoding of the specific SImessage is successful.

In one alternative, the method may further include, when the SI messagedecoding is successful after the SI message decoding is attempted forthe remaining subframe instances, updating, by the processing device,the SI submframebmp for the specific SI message for the currentlyselected base station stored in the memory according to detection anddecoding status in radio frames and subframes in which the specific SImessage was transmitted by the currently selected base station.

In accordance with an aspect of the present invention, an apparatus fordecoding system information may include a processing device configuredto: determine whether a system information block (SIB) Presence Bitmapfor a currently selected base station is stored in a memory of awireless communication device associated with the processing device; andcontrol SIB decoding for the currently selected base station accordingto either a SIB Presence Bitmap of a last serving base station or theSIB Presence Bitmap for the currently selected base station stored inthe memory selected as a selected SIB Presence Bitmap, based on a resultof the determining whether the SIB Presence Bitmap is in the memory.

In one alternative of the apparatus, the processing device may beconfigured to: determine whether the SIB decoding is successful; andwhen the decoding is determined to be successful, update the SIBPresence Bitmap for the currently selected base station stored in thememory according to detection and decoding status in radio frames andsubframes in which a SIB was transmitted by the currently selected basestation.

In one alternative of the apparatus, the processing device may beconfigured to, when the SIB decoding is determined to be unsuccessful,determine whether SIB decoding was attempted for all instances of theSIB within a SIB periodicity.

In one alternative of the apparatus, the processing device may beconfigured to: control decoding of a SI message for the currentlyselected base station according to scheduling information for SImessages extracted from a SIB decoded from the currently selected basestation; determine whether a SI subframe bitmap (subframebmp) for aspecific SI message selected for decoding for the currently selectedbase station is stored in the memory; and control SI message decodingfor the specific SI message for the currently selected base stationaccording to a SI subframebmp of the last serving base station or the SIsubframebmp for the currently selected base station stored in the memoryselected as a selected SI subframebmp, based on a result of thedetermining whether the SI subframebmp is in the memory.

In accordance with an aspect of the present invention, a method forwireless communication may include controlling, by a processing device,receiving of system information (SI) based on information from a memoryabout a radio frame and subframe in which another SI is detected at awireless communication device associated with the processing device alast time when the wireless communication device camped on a basestation; and storing in the memory, by the processing device, a systemframe number (SFN) in which a system information block (SIB) of theanother SI is detected for the base station.

In one alternative, the method for wireless communication may include,when the processing device performs selection of, reselection of orhandover to another base station and the memory indicates at least onesystem frame number (SFN) in which the wireless communication devicedetected a system information block (SIB) when the wirelesscommunication device previously camped on the another base station, theprocessing device controls decoding of the SIB only in the at least oneSFN. In a further alternative, the at least one SFN is stored as aPresence Bitmap for the another base station

In one alternative, the method for wireless communication may include,when the processing device performs selection of, reselection of orhandover to another base station and a system frame number (SFN) inwhich the wireless communication device detected a system informationblock (SIB) for the another base station is not indicated in the memory,the processing device controls decoding of the SIB for the another basestation in a plurality of SFNs for a most recent base station served bythe wireless communication device indicated in the memory as a PresenceBitmap.

In one alternative of the method for wireless communication, theprocessing device may control turning off at least one subsystem of thewireless communication device for a subframe in a system frame number(SFN) other than a SFN indicated in the memory in which the wirelesscommunication device is to decode a system information block (SIB). In afurther alternative, the subframe in the system frame number (SFN) otherthan the SFN in which the wireless communication device is to decode thesystem information block (SIB) is indicated in the memory as a PresenceBitmap.

In one alternative, the method for wireless communication may include,when the processing device performs selection of, reselection of orhandover to another base station and the memory indicates a bit mapSI-subframebmp for at least one SI message detected in a previous campon by the wireless communication device, the processing device controlsdecoding of another SI message in at least one subframe corresponding toat least one bit set in the SI-subframebmp for the SI-window for theanother SI message.

In one alternative of the method for wireless communication, theprocessing device may control turning off at least one subsystem of thewireless communication device for at least one subframe corresponding toat least one bit in a SI window not set in a SI-subframebmp indicated inthe memory in which decoding of an SI message by the processing deviceis not controlled.

In one alternative of the method for wireless communication, the systeminformation block (SIB) of the another SI is detected for the basestation based on a Physical Downlink Control Channel (PDCCH) with aSystem Information-Radio Network Temporary Identifier (SI-RNTI).

In one alternative, the method for wireless communication may include,when decoding by the processing device of a system information block(SIB) for another base station in a system frame number (SFN) of aplurality of SFNs for the another base station, the plurality of SFNsbeing stored in the memory as a Presence Bitmap for the another basestation, is not successful, the processing device controls based on thePresence Bitmap decoding of the SIB in each of the plurality of SFNs forwhich decoding of the SIB was not attempted until the decoding of theSIB is successful.

In one alternative, the method for wireless communication may include,when a system frame number (SFN) in which the wireless communicationdevice detected a system information block (SIB) for any base stationother than a base station being served by the wireless communicationdevice is not indicated in the memory and decoding by the processingdevice of the SIB using a plurality of system frame number (SFNs) forthe base station being served indicated in a Presence Bitmap in thememory is not successful, the processing device controls decoding of theSIB in a plurality of SFNs in which the SIB may be present.

In one alternative, the method for wireless communication may include,when a system information (SI) message is received for another basestation by the processing device, the processing devices controlsstoring in the memory of a subframe number in a system informationwindow in which the processing device detects the SI message based onsuccessful decoding of a Physical Downlink Control Channel (PDCCH) witha System Information-Radio Network Temporary Identifier (SI-RNTI).

In one alternative, the method for wireless communication may include,when a system information (SI) message is detected by the processingdevice in a system information window, the processing device controlsstoring of subframe number information in the SI-window in a bitmapformat. In a further alternative, in the bitmap format, SI-subframebmpbit₀ represents 0th subframe in the SI-window and bit_(n) represents nthsubframe in the SI-window. In still a further alternative, theSI-subframebmp is maintained separately for each SI message.

In one alternative, the method for wireless communication may include,when decoding by the processing device of a SI message for another basestation in subframes according to a SI-subframebmp of a SI-windowindicated in the memory is not successful, the processing devicecontrols decoding of the SI message in all subframes in the SI-window.

In one alternative, the method for wireless communication may include,when subframe information in a SI-subframebmp for a SI message foranother base station is not indicated in the memory, the processingdevice controls decoding of the SI message using a SI-subframebmp of alast base station served by the wireless communication device indicatedin the memory.

In accordance with an aspect of the present invention, an apparatus forwireless communication may include a processing device configured tocontrol: receiving of system information (SI) based on information froma memory about a radio frame and subframe in which another SI isdetected at a wireless communication device associated with theprocessing device a last time when the wireless communication devicecamped on a base station; and storing in the memory of a system framenumber (SFN) in which a system information block (SIB) of the another SIis detected for the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional mobile wireless communication system.

FIG. 2 illustrates the high level air-interface structure of the 3GPPLTE wireless communication system.

FIG. 3 illustrates an example mapping of the MIB to the radio frames in3GPP LTE wireless communication system.

FIG. 4 illustrates an example mapping of the SIB 1 to the radio framesin 3GPP LTE wireless communication system.

FIG. 5 illustrates an example mapping of the different SIBs to SImessages with different periodicity in 3GPP LTE wireless communicationsystem.

FIG. 6 illustrates an example mapping of the SI messages to SI-windowswith different dynamic scheduling within the windows in 3GPP LTEwireless communication system.

FIGS. 7-A and 7-B illustrate an example flow diagram for processingsteps according to aspects of the present invention.

FIG. 8 illustrates a wireless mobile station diagram, which may beemployed with aspects of the invention described herein.

FIG. 9 illustrates an application processor subsystem for a wirelessmobile station, which may be employed with aspects of the inventiondescribed herein.

FIG. 10 illustrates a baseband subsystem for a wireless mobile station,which may be employed with aspects of the invention described herein.

FIG. 11 illustrates an RF subsystem for a wireless mobile station, whichmay be employed with aspects of the invention described herein.

DETAILED DESCRIPTION

The foregoing aspects, features and advantages of the present inventionwill be further appreciated when considered with reference to thefollowing description of exemplary embodiments and accompanyingdrawings, wherein like reference numerals represent like elements. Indescribing the exemplary embodiments of the invention illustrated in theappended drawings, specific terminology will be used for the sake ofclarity. However, the invention is not intended to be limited to thespecific terms used

As per the 3GPP LTE wireless communication system specifications, whenacquiring an SI message, the client terminal shall:

-   -   determine the start of the SI-window for the concerned SI        message as follows:        -   for the concerned SI message, determine the number n which            corresponds to the order of entry in the list of SI messages            configured by SchedulingInformation IE in the SIB1;        -   determine the integer value x=(n−1)*w, where w is the            si-WindowLength;        -   the SI-window starts at the subframe #a, where a=x mod 10,            in the radio frame for which SFN mod T=FLOOR(x/10), where T            is the si-Periodicity of the concerned SI message and FLOOR(            ) is defined as a function that rounds its argument to the            nearest integer towards negative infinity;            The SI-window length field in the SIB1 is defined as having            one the following values: 1, 2, 5, 10, 15, 20, and 40 ms.

As per the 3GPP LTE wireless communication system specifications, aRadio Network Temporary Identifier (RNTI) is used for identifyingdifferent UEs (User Equipment) and various other types of information.The SI-RNTI is used for identifying the PDSCH that carries the SIpayload. The presence of PDSCH that contains the SIB1 or other SImessages is indicated by the Physical Downlink Control Channel (PDCCH).If a PDCCH is decoded with the identifier SI-RNTI, it is an indicationthat a PDSCH carrying the SIB1 or SI payload is present in the subframein which the PDCCH with SI-RNTI is decoded. The PDSCH decoding in thatsubframe may be successful or not. If the PDSCH decoding is notsuccessful, the client terminal may save the channel soft bits (alsoknown as log likelihood ratios) for combining with future repetitions orretransmissions of the same payload.

The 3GPP LTE wireless communication system uses Hybrid Automatic RepeatRequest (HARD) with Incremental Redundancy. The Initial transmission ofa block of data and the subsequent retransmissions may use differentRedundancy Versions (RV) for improved decoding performance. The RV ofthe transmissions is indicated by the network in the PDCCH. For the caseof SI message transmission, repeated transmissions are used without anyACK/NACK to achieve the benefit of combining over multipletransmissions. The RV of each SI transmission may be indicatedexplicitly by the network in the PDCCH or may be derived implicitly bythe client terminal as follows.

As per 3GPP LTE wireless communication system specifications, the RV ofthe received downlink assignment for a particular subframe is determinedby:RV _(K)=ceiling(3/2*k)modulo 4where k depends on the type of system information message.For SIB1 message,k=(SFN/2)modulo 4For other SI messages,k=i modulo 4, i=0,1, . . . , n _(s) ^(w)−1,where i denotes the subframe number within the SI window n_(s) ^(w).

When the client terminal performs cell selection, cell reselection orhandover i.e., in general when transitioning from one eNB to anothereNB, it performs time synchronization with the target eNB and decodesthe MIB. Once the MIB is decoded, the client terminal may synchronizethe client terminal radio frame number and timing to that of the targeteNB. Once the client terminal decodes and derives the radio frame numberfrom the MIB, it maintains the radio frame number by incrementing theradio frame number modulo 1024 since the frame number is defined to be a10-bit number.

Based on the 3GPP LTE wireless communication system specifications, theSIB1 decoding may be attempted in all the defined periodicity for SIB1which is a fixed schedule with a periodicity of 80 ms and repetitionsmade within 80 ms. The first transmission of SIB1 is scheduled insubframe #5 of radio frames for which the SFN mod 8=0, and repetitionsare scheduled in subframe #5 of all other radio frames for which SFN mod2=0. An example of this is shown in FIG. 4.

The eNB may transmit the SIB1 in subframe #5 of all radio frames forwhich SFN mod 2=0. The eNB may transmit the SIB1 in subframe #5 of someradio frame for which SFN mod 2=0, but may transmit at least one SIB1within 80 ms.

According to an aspect of the present invention, when the clientterminal detects SIB1 is scheduled for a given cell (based on PDCCH withSI-RNTI), it may store the SFN in which it has detected the SIB1transmission. The SFN for SIB1 presence may be SFN mod 8=0 and/or SFNmod 8=2 and/or SFN mod 8=4 and/or SFN mod 8=6 and these SFNs arereferred to as P1, P2, P3 and P4 respectively. The eNB may transmit inall four SFNs P1, P2, P3, and P4 or only a subset of them. The clientterminal stores the actual SFN instances in which the SIB1 presence isdetected for the given cell. This may be stored as a 4-bit bitmap,namely, “SIB1 Presence Bitmap” corresponding to each of the fourinstances P1, P2, P3 and P4. If an SIB1 is scheduled in P1, thecorresponding bit is set regardless of whether the decoding issuccessful or not. Similarly, if an SIB1 is scheduled in P2, thecorresponding bit is set regardless of whether the decoding issuccessful or not, and so on for P3 and P4.

According to another aspect of the present invention, when the clientterminal performs cell selection or cell reselection or handover to atarget eNB referred herein as eNB_(t1), if the client terminal haspreviously visited eNB_(t1) and the client terminal has the storedinformation of the SFNs in which the client terminal detected SIB1during the previous camp on the same eNB (eNB_(t1)), i.e., previouslysaved SIB1 Presence Bitmap for that cell is available, then the clientterminal may attempt to receive the SIB1 only in the SFNs according tothe stored SIB1 Presence Bitmap for the eNB_(t1).

According to another aspect of the present invention, when the clientterminal attempts to receive SIB1 in eNB_(t1) based on the stored SIB1Presence Bitmap and the SIB1 receive operation in eNB_(t1) is notsuccessful, the client terminal may attempt to decode SIB1 in all theSIB1 SFNs where it may be mapped (P1, P2, P3, P4) in eNB_(t1) if thedecoding was not already attempted in all four instances based on thesaved SIB1 Presence Bitmap.

According to another aspect of the present invention, when the clientterminal performs cell selection or cell reselection to an eNB sayeNB_(t2), if the client terminal does not have the stored SIB1 PresenceBitmap for the SFNs in which a neighbor cell transmits the SIB1, thenthe client terminal may attempt to receive the SIB1 in that cell in theSFNs according to the stored SIB1 Presence Bitmap from most recentserving cell.

According to another aspect of the present invention, when the clientterminal does not have stored SIB1 Presence Bitmap information for anyneighbor cell, and the SIB1 decode attempt using the SIB1 PresenceBitmap SFNs for serving eNB also fails then the client terminal mayattempt to receive SIB1 in all the SFNs where SIB1 may be mapped (P1,P2, P3 and P4).

According to an aspect of the present invention, the client terminal mayturn off some of its subsystems for the subframe #5 in SIB1 SFNs P1 orP2 or P3 or P4 where the client terminal does not attempt to receiveSIB1 as per the stored SIB1 Presence Bitmap and SFN periodicity.

Based on the 3GPP LTE wireless communication system specifications,unlike the SIB1, the SI messages reception may be attempted in all thesubframes within the SI-window. Typically the client terminal mayattempt to receive SI messages in all the subframes within theSI-window. The present invention provides a method for the clientterminal to receive the SI messages based on the stored informationabout radio frames and subframes in which the client terminal detectedthe SI messages when the client terminal camped on the eNB last time.

According to an aspect of the present invention, when the clientterminal receives SI messages in an eNB, the client terminal may storethe subframe numbers in the SI-window in which it detected the SImessages based on successful decoding of PDCCH with SI-RNTI.

According to an aspect of the present invention, when the clientterminal detects an SI message in an SI-window, the client terminal maystore the subframe number information in the SI-window in a bitmapformat, namely, SI-subframebmp. Bit₀ may represent the 0^(th) subframein the SI-window and bit_(n) may represent n^(th) subframe in theSI-window. According to another aspect of the present invention, theSI-subframebmp may be maintained separately for each SI message.

According to another aspect of the present invention, when the clientterminal performs cell selection or cell reselection or handover to an aneighbor cell, if the client terminal has previously visited that celland the client terminal has the stored SI-subframebmp in which theclient terminal detected the SI messages during the previous camp on,then the client terminal may attempt to receive the SI messages in thesubframes corresponding to the bits set in the SI-subframebmp for theSI-window for the specific SI message.

According to another aspect of the present invention, when the clientterminal attempts to receive SI messages for a neighbor cell insubframes according to the stored SI-subframebmp of SI-window and the SImessage receive is not successful, the client terminal may attempt toreceive SI message in all the subframes in the SI-window.

According to another aspect of the present invention, when the clientterminal does not have stored subframe information in SI-subframebmp forthe specific SI message for a given neighbor cell, the SI receptionusing the previously stored SI-subframebmp of the last serving cell maybe used.

According to an aspect of the present invention, the client terminal mayturn off some of its subsystems for the subframes corresponding to bitsin the SI-window which are not set in the SI-subframebmp where theclient terminal does not attempt to receive SI messages.

Aspects of the invention to turn off some of the subsystems forsubframes, where the client terminal does not attempt to receive SIB1 orSI messages based on stored SIB1 Presence Bitmap or based on storedSI-subframebmp, enable the client terminal to reduce the powerconsumption significantly, which is very essential for any batteryoperated device.

The flow diagram 700 contained in FIG. 7-A and FIG. 7-B illustrate anexemplary SIB1 and SI decoding method according to the various aspectsof the present invention. The processing relevant to the presentinvention begins in the processing stage 702 where the cell for whichthe System Information is required is identified according to the 3GPPLTE wireless communication system specifications. At processing stage704 the MIB decoding is performed for the selected cell. At processingstage 706 a determination is made whether previously saved SIB1 PresenceBitmap is available for the currently selected cell. If the previouslysaved SIB1 Presence Bitmap is available for the currently selected cell,at processing stage 708 it is selected for scheduling SIB1 decoding insubsequent steps. If the previously saved SIB1 Presence Bitmap is notavailable for the currently selected cell, at processing stage 710 SIB1Presence Bitmap of the last serving cell is selected for scheduling SIB1decoding in subsequent steps. After completion of processing at stages708 or 710, the processing continues at stage 712. At processing stage712 the SIB1 decoding is scheduled for the currently selected cell inthe radio frames and subframes according to the SIB1 Presence Bitmapselected in earlier stages. At processing stage 714 a determination ismade whether the SIB1 decoding is successful. If the SIB1 decoding issuccessful, the processing jumps to the processing stage 722 where theSIB1 Presence Bitmap for the currently selected cell is updatedaccording to the detection and decoding status in radio frames andsubframes where the SIB1 was transmitted by the eNB. Returning toprocessing stage 714, if SIB1 decoding is not successful the processingcontinues at processing stage 716. At processing stage 716 adetermination is made whether decoding for all instances of SIB1 withinthe SIB1 periodicity are attempted or not. If the decoding for all theinstances of SIB1 within the SIB1 periodicity are attempted, theprocessing jumps to the reference point A in 726. If the decoding forall the instances of SIB1 within the SIB1 periodicity are not attempted,the processing continues at processing stage 718 where the SIB1 decodingis scheduled for the remaining SIB1 instances where the SIB1 decodingwas not scheduled in processing stage 712. Next at processing stage 720a determination is made whether the SIB1 decoding is successful or not.If the SIB1 decoding is not successful, the processing jumps to thereference point A in 726. If the SIB1 decoding is successful, theprocessing moves to the processing stage 722 where the SIB1 PresenceBitmap for the currently selected cell is updated according to thedetection and decoding status in radio frames and subframes where theSIB1 was transmitted by the eNB. Next at processing stage 724 thedecoded SIB1 is parsed and the scheduling information for the SImessages is extracted. The processing moved to the reference point A in726.

The flow diagram 700 continues in FIG. 7-B at reference point A in 726.At processing stage 728, the decoding of a specific SI message for thecurrently selected cell is scheduled according to the schedulinginformation extracted from the SIB1 for the currently selected cell. Atprocessing stage 730 a determination is made whether a previously savedSI-subframebmp is available for the specific SI message selected fordecoding for the currently selected cell. If the previously savedSI-subframebmp is available for the currently selected cell, atprocessing stage 732 it is selected for scheduling SI message decodingin subsequent steps. If the previously saved SI-subframebmp is notavailable for the currently selected cell, at processing stage 734, theSI-subframebmp of the last serving cell is selected for scheduling SImessage decoding in subsequent steps. After completion of processing atstages 732 or 734, the processing continues at stage 736. At processingstage 736 the specific SI message decoding is scheduled for thecurrently selected cell in the radio frames and subframes according tothe selected SI-subframebmp selected in earlier stages. At processingstage 738 a determination is made whether the specific SI messagedecoding is successful. If the specific SI message decoding issuccessful, the processing jumps to the processing stage 746 where theSI-subframebmp for the specific SI message of the currently selectedcell is updated according to the detection and decoding status in radioframes and subframes where the specific SI message was transmitted bythe eNB. Returning to processing stage 738, if specific SI messagedecoding is not successful the processing continues at processing stage740. At processing stage 740 a determination is made whether allinstances of the specific SI message within the SI-window are attemptedor not. If all the instances of the specific SI message within theSI-window are attempted, the processing jumps to the stage 748 where theprocessing for decoding the specific SI message terminates. If all theinstances of the specific SI message within the SI-window are notattempted, the processing continues at processing stage 742 where thespecific SI message decoding is scheduled for the remaining SI messageinstances where the specific SI message decoding was not scheduled inprocessing stage 736. In an alternative embodiment, at processing stage742 the specific SI message decoding is performed for the remaining SImessage instances where the specific SI message decoding was notscheduled in processing stage 736, until a determination is made thatthe specific SI message decoding is successful. Next at processing stage744 a determination is made whether the specific SI message decoding issuccessful or not. If the specific SI message decoding is notsuccessful, the processing jumps to stage 748 where the processing fordecoding the specific SI message terminates. If the specific SI messagedecoding is successful, the processing moves to the processing stage 746where the SI-subframebmp for the specific SI message for the currentlyselected cell is updated according to the decoding status in radioframes and subframes where the specific SI message was transmitted bythe eNB. Finally, the processing for specific SI message decodingterminates at stage 748.

Note that the processing for decoding additional SI messages, ifpresent, is identical to the processing from processing stages 728 to748. According to the aspects of the present invention, theSI-subframebmp is maintained separately for each of the SI messagespresent in the currently selected cell. The processing for decoding ofthe different SI messages of the selected cell may be performed inparallel or sequentially.

By way of example only, the above-described method may be implemented ina receiver, e.g., a user device such as a wireless mobile station (MS)12 as shown in FIG. 1.

As shown in FIG. 8, MS 100 may include an application processorsubsystem 101, baseband subsystem 102 and a radio frequency (RF)subsystem 104 for use with a wireless communication network. Adisplay/user interface 106 provides information to and receives inputfrom the user. By way of example, the user interface may include one ormore actuators, a speaker and a microphone. In some mobile devices,certain combination of the application processor subsystem 101, thebaseband subsystem 102 and the RF subsystem 104 are all integrated asone integrated chip.

The application processor subsystem 101 as shown in FIG. 9 may include acontroller 108 such as a microcontroller, other processor or circuitry.The baseband subsystem 102 as shown in FIG. 10 may include a controller118 such as a microcontroller, other processor or circuitry. The RFsubsystem 104 as shown in FIG. 11 may include a controller 128 such as amicrocontroller, other processor or circuitry. The controller 108desirably handles overall operation of the MS 100. This may be done byany combination of hardware, software and firmware running on thecontroller 108. Such combination of hardware, software and firmware mayembody any methods in accordance with the aspects of the presentinvention.

In FIG. 10 the peripherals 114 such as a full or partial keyboard, videoor still image display, audio interface, etc may be employed and managedthrough the controller 108.

Aspects of the present invention may be implemented in firmware of thecontroller 108 of the application processor and/or the controller 118 ofthe baseband subsystem as shown in FIG. 8. In another alternative,aspects of the present invention may also be implemented as acombination of firmware and hardware of the application processorsubsystem 101 and/or the baseband subsystem 102. For instance, signalprocessing functionality of any or all of the FIG. 10 may be implementedin firmware and/or software, which is executed by the system hardware.It may be part of the baseband subsystem, the receiver subsystem or beassociated with both subsystems. In one example, the controller 118and/or the signal processor 110 may include or control the protocolentity circuitry. The software may reside in internal or external memoryand any data may be stored in such memory. The hardware may be anapplication specific integrated circuit (ASIC), field programmable gatearray (FPGA), discrete logic components or any combination of suchdevices. The terms controller and processor are used interchangeablyherein.

The consumer electronics devices that may use the aspects of theinvention may include smartphones, tablets, laptops, gaming consoles,cameras, video camcorders, TV, car entertainment systems, etc.

Although aspects of the invention herein have been described withreference to particular embodiments, it is to be understood that theseembodiments are merely illustrative of the principles and applicationsof the aspects of the present invention. It is therefore to beunderstood that numerous modifications may be made to the illustrativeembodiments and that other arrangements may be devised without departingfrom the spirit and scope of the aspects of the present invention asdefined by the appended claims. Aspects of each embodiment may beemployed in the other embodiments described herein.

The invention claimed is:
 1. A method for wireless communicationcomprising: controlling, by a processing device, receiving of systeminformation (SI) based on information from a memory about a radio frameand subframe in which another SI is detected at a wireless communicationdevice associated with the processing device a last time when thewireless communication device camped on a base station; storing in thememory, by the processing device, a system frame number (SFN) in which asystem information block (SIB) of the another SI is detected for thebase station; and when SIB decoding for the base station is determinedto be unsuccessful for a given system information block (SIB) accordingto a Presence Bitmap for the base station stored in the memory,controlling, by the processing device, updating the Presence Bitmap forthe base station in accordance with a given SFN for which the SIBdecoding of the given SIB is determined to be unsuccessful; controlling,by the processing device, decoding of another SI message in at least onesubframe corresponding to at least one bit set in a SI-subframebitmap.2. The method of claim 1, wherein, when the processing device performsselection of, reselection of or handover to another base station and thememory indicates at least one system frame number (SFN) in which thewireless communication device detected a second system information block(SIB) when the wireless communication device previously camped on theanother base station, the processing device controls decoding of thesecond SIB only in the at least one SFN.
 3. The method of claim 1,wherein, when the processing device performs selection of, reselectionof or handover to another base station and a second system frame number(SFN) in which the wireless communication device detected a secondsystem information block (SIB) for the another base station is notindicated in the memory, the processing device controls decoding of thesecond SIB for the another base station in a plurality of SFNs for amost recent base station served by the wireless communication deviceindicated in the memory as a Presence Bitmap.
 4. The method of claim 1,wherein the processing device controls turning off at least onesubsystem of the wireless communication device for a subframe in asecond system frame number (SFN) other than a second SFN indicated inthe memory in which the wireless communication device is to decode asecond system information block (SIB).
 5. The method of claim 1, furthercomprising: controlling, by the processing device, performing selectionof, reselection of or handover to another base station, in which thememory indicates a bit map SI-subframebmp for at least one SI messagedetected in a previous camp on by the wireless communication device. 6.The method of claim 1, wherein the processing device controls turningoff at least one subsystem of the wireless communication device for atleast one subframe corresponding to at least one bit in a SI window notset in a SI-subframebmp indicated in the memory in which decoding of anSI message by the processing device is not controlled.